• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>International Journal of Heat and Mass Transfer >A novel time strip flow visualisation technique for investigation of intermittent dewetting and dryout in elongated bubble flow in a microchannel evaporator
【24h】

A novel time strip flow visualisation technique for investigation of intermittent dewetting and dryout in elongated bubble flow in a microchannel evaporator

机译：一种新型的带状流可视化技术，用于研究微通道蒸发器中细长气泡流中的间歇性脱湿和变干

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

A flow visualisation study of flow boiling of R245fa in silicon multi-microchannels at low mass flux and moderate heat flux has been carried out with a high speed digital camera. The micro-evaporator had 67 channels of length 20 mm, width 223 μm, and height 680 μ.m while the fin width between adjacent channels was 80 μm. The base heat flux ranged from 2 to 26 W cm~(-2) for a mass velocity of 100 kg s~(-1) m~(-2), resulting in exit vapour qualities ranging from 10% to 70%. In particular, a novel time strip technique was developed to analyse the recorded image sequences and significantly highlight the various phenomena occurring along given channels. Notably, this technique was able to reveal profound details regarding the intermittent dryout mechanism of liquid films trapped between the elongated bubbles and the heated channel walls. The results show that the intermittent dryout of the evaporating liquid film is comprised of four stages with distinct time scales and dynamics: (i) the growth of liquid film thinning perturbations to a critical amplitude causing the rupture of the metastable liquid film, (ii) a dewetting stage involving expanding dry spots leading to a rivulet flow regime, (iii) evaporation of the rivulets leading to full dryout, and (iv) a rewetting stage. This intermittent dryout mechanism appears to explain the many seemingly contradictory heat transfer coefficient trends observed with changes in vapour quality in microchannels, thus resolving an important heat transfer dilemma. Furthermore, since dryout is an undesirable event during the practical application of a microchannel evaporator, it is important to delay or even suppress the initial rupture of the liquid film that leads to dryout. This can be achieved by manufacturing or treating the channel surfaces to be highly wettable with the chosen refrigerant.
机译：用高速数码相机对低质量通量和中等热通量的硅多微通道中R245fa的流动沸腾进行了流动可视化研究。微蒸发器具有67个通道，其长度为20mm，宽度为223μm，高度为680μm，而相邻通道之间的翅片宽度为80μm。对于100 kg s〜（-1）m〜（-2）的质量速度，基本热通量在2到26 W cm〜（-2）的范围内，导致出口蒸气质量在10％到70％的范围内。特别是，开发了一种新颖的时间条技术来分析记录的图像序列并显着突出显示沿给定通道发生的各种现象。值得注意的是，该技术能够揭示有关滞留在细长气泡和加热通道壁之间的液膜的间歇性变干机制的深刻细节。结果表明，蒸发液膜的间歇性变干包括四个阶段，分别具有不同的时间尺度和动力学：（i）液膜变薄扰动的增长到临界幅度，导致亚稳液膜破裂；（ii）除湿阶段包括扩大干点导致小溪流动状态，（iii）小溪蒸发导致完全变干，以及（iv）再湿阶段。这种间歇性的变干机制似乎可以解释随着微通道中蒸汽质量的变化而观察到的许多看似矛盾的传热系数趋势，从而解决了一个重要的传热难题。此外，由于在微通道蒸发器的实际应用期间变干是不希望的事件，所以重要的是延迟或什至抑制导致变干的液膜的初始破裂。这可以通过制造或处理通道表面使其高度被所选制冷剂润湿来实现。

著录项

  • 来源
    《International Journal of Heat and Mass Transfer》 |2010年第22期|p.4809-4818|共10页
  • 作者

    Navid Borhani; Bruno Agostini; John Richard Thome;

  • 作者单位

    Heat and Mass Transfer Laboratory (LTCM), Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland;

    ABB Switzerland Ltd, Corporate Research, Segelhofstrasse 1K, CH-5405 Baden 5 Dattwil, Switzerland;

    rnHeat and Mass Transfer Laboratory (LTCM), Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    microchannel evaporator; dryout; flow visualisation;

    机译：微通道蒸发器干out流可视化;

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号